The present disclosure relates to a particle sorting apparatus and a particle sorting method. More particularly, the present disclosure relates to a technology for sorting and recovering particles based on a result of an optical analysis.
In the related art, to analyze biologically-relevant particles such as cells, microorganisms and liposomes, an optical measuring method using a flow cytometry (flow cytometer) is utilized. The flow cytometer is an analyzer for irradiating particles flowing through a flow path formed within a flow cell or a microchip with light and detecting fluorescence or a scattered light emitted from each particles.
One of the flow cytometers has a function to sort and recover the particles having a specific property based on a result of analysis. In particular, an apparatus for sorting cells is called as “a cell sorter”. As a sorting method used in the cell sorter, a liquid droplet charging method of charging and separating liquid droplets containing particles is mainly used (for example, see Japanese Patent Application Laid-open No. 2009-145213). In an apparatus using the liquid droplet charging method, a fluid discharged from a flow cell or a microchip is liquefied, and liquid droplets are positively (+) or negatively (−) charged, changed their traveling directions by a deflection plate and recovered by a predetermined container.
However, the sorting method such as the liquid droplet charging method where the liquid droplets are formed is undesirably affected by a change in a measurement environment or a liquid pressure change. A particle sorting apparatus where particles are sorted within a microchip has then been proposed in the related art (see Japanese Patent Application Laid-open No. 2012-127922). The particle sorting apparatus described in Japanese Patent Application Laid-open No. 2012-127922 sucks particles to be recovered into a negative pressure suction unit within the microchip. Therefore, forming liquid droplets and charging are unnecessary, whereby stable sorting can be done at a high speed without damaging the particles.
The particle sorting apparatus in the related art is generally controlled to acquire the particles to be recovered after a predetermined time from detection at a light detecting unit. The time to acquire the particles from detection is set in advance based on a liquid pressure, a distance from a detection position to a sorting position, etc. However, by the controlling method where an arrival time is fixed in this way, a purity of recovered particles or an acquisition rate is undesirably lowered, once a flow speed of the particles is changed.
On the other hand, the apparatus described in Japanese Patent Application Laid-open No. 2009-145213 detects a migration speed of each particle and controls a timing to charge each particle based on the migrating speed in order to prevent the purity from lowering due to the change in the flow speed of the particles. In the liquid droplet charging method, it may only determine that the respective particles belong to which liquid droplets. However, in the apparatus for sorting within the microchip, fluid mechanism characteristics may be considered as well as attributes of adjacent particles. Here, the “attributes of particles” mean that the particles are to be sorted or not, and the “fluid mechanism characteristics” mean a counter flow generated when a pulse signal is risen for acquisition operation.
In the liquid droplet charging method, the liquid droplets are controlled. However, in the method for sorting within the microchip described in Japanese Patent Application Laid-open No. 2012-127922, the respective particles should be controlled. In addition, there are differences in a path to arrive at an acquisition position and a factor affecting the arrival of the particles between the liquid droplet charging method and the method for sorting within the microchip. For the above reasons, the technology described in Japanese Patent Application Laid-open No. 2009-145213 is not simply applied to the apparatus for sorting within the microchip described in Japanese Patent Application Laid-open No. 2012-127922.
It is desirable to provide a particle sorting apparatus and a particle sorting method for effectively sorting particles within microchip.